The research of the McArdle Laboratory for Cancer Research is divided into 3 broad categories: Biochemical Studies in Chemical Carcinogenesis, Molecular Biology and Genetics of Tumor Viruses, and Regulatory Mechanisms in Tumor Biology. The chemical carcinogenesis program encompasses a broad fundamental approach to the chemistry, biochemistry, and biology of tumor initiation and promotion due to chemicals. The overall objective of these studies is a detailed knowledge of chemical carcinogenesis that will facilitate the identification of the stages at which controls can be imposed on the process. The studies in tumor virology encompass the molecular biology and genetics of avian and murine RNA tumor viruses and of two primate DNA tumor viruses, simian virus 40 and Epstein-Barr virus. Of special interest are the DNA genomes of these viruses and problems related to mechanisms and sites of integration, control of transcription, and mechanisms of transformation by the virus genomes. The tumor biology program is a multidisciplinary approach to regulatory mechanisms that influence the growth, replication, and differentiation of normal and cancer cells. The approaches include studies of DNA and chromatin replication, transcription and processing of mRNA, the composition and function of cellular membranes, the characterization of proteins involved in both nucleic acid and cellular replication, and the mechanisms of differentiation of lambda phage and various cell types.